A copper coil heat exchanger inside the heat exchanger tank, which is partially filled with canola oil. The float switch sits in the tank’s upper left corner, and a temperature probe is located in the center on the left side.

The seed sorter/cleaner removes chaff and other debris from the seeds before they are fed to the seed crusher.

Seed goes into the top of the seed crusher where it is crushed. The feed meal by-product is dumped into a bucket, and canola oil comes out of a chute on the left.

Feed meal coming out of the seed crusher. This is the by-product that is sold to farmers as nutritious livestock feed.

Project manager Ben Doon stands next to a filter that removes impurities from the raw canola oil.

Exterior view of the CCBD plant. The grey tank contains methanol for making biodiesel. The smaller green tank contains petroleum diesel. Mixed (finished) biodiesel is stored in the larger green tank, where it is dispensed directly to the county’s fleet of vehicles. The solar thermal collectors can be seen on the roof. The large bin on the right stores raw canola seed.

Beginner

The remote and tiny enclave of Mesita, at the southern edge of Colorado’s San Luis Valley, is not the sort of place where you’d expect to find a pioneering renewable energy facility. But at the edge of this isolated outpost sits Costilla County Biodiesel (CCBD), producing biodiesel from local crops—while part of the plant’s energy is produced with sunshine.

CCBD is unique not only because of its remote location, but also because it is one of the few medium-scale biodiesel production facilities in the country. In 2010, my company, Solar Gain Services (SGS), designed and installed a solar thermal system to help the plant reduce its reliance on utility electricity—thus using renewable energy to power the production of a renewable fuel.

Raising Renewables

CCBD was conceived in 2001 by County Commissioner Joe Gallegos, who was looking for ways to create local economic development. Gallegos recognized that he needed to build upon the only strong private industry in the county: agriculture. He searched for a way to add value to local crops, and also studied whether this could be combined with the burgeoning growth of the RE industry. A feasibility study brought the idea of a biodiesel plant to the forefront—the county government consumes roughly 100,000 gallons of diesel annually to maintain its nearly 3,500 miles of roads. Though canola wasn’t being grown locally at the time, a study showed that the crop was ideally suited to southern Colorado’s climate, and was similar to seed crops that farmers were already accustomed to growing. Additionally, Gallegos discovered that the biodiesel process would churn out a nutritious by-product that could be sold to local ranchers for livestock feed.

In 2004, Project Manager Ben Doon procured a $150,000 USDA Rural Development grant to purchase equipment. Costilla County erected the building, and production began in 2006 with basic equipment.

“It was definitely not a turnkey facility,” says Doon. “A lot of our small-scale production equipment was gathered from around the globe, where similar facilities exist. The equipment was procured piecemeal, and we had to figure out how it worked, often making modifications. Slowly, we tied all the equipment together to create a semi-automated production line. But in the beginning, everything was run by hand. Materials were moved through the line using 5-gallon buckets and hand pumps. Now, seed is transferred with augers and liquid is pumped through pipes.”

Since those early days, production has grown slowly but steadily. Today, CCBD makes roughly 50,000 gallons of biodiesel per year—about half the annual output that Doon would like to see in the next several years.

Renewables Powering Renewables

Since Costilla County has no natural gas pipelines, all of the facility’s energy comes from electricity. With more than 300 days of sunshine and clear air, the San Luis Valley has one of the best solar resources in the country. As the plant’s production increased and kinks were worked out, Doon thought about how solar energy could be used to decrease production costs while reducing the facility’s carbon footprint.

He wondered whether solar could be used to heat canola oil to about 185°F to make biodiesel. Each 100-gallon batch was heated using electricity, from starting temperatures as low as 50°F. This consumed a lot of electrical energy, and also took nearly an hour, creating a production bottleneck. Doon asked SGS to design a solar thermal system and draft a proposal for grant funding. The grant was approved, and was received from the Governor’s Energy Office of Colorado in 2010.

The solar thermal system uses nine roof-mounted Sun Earth EC-32 flat-plate collectors and a copper-coil heat exchanger inside a custom, insulated 400-gallon tank. The solar collector loop uses propylene glycol to prevent freezing during winter, while flow is controlled with a Viessmann pump station and a Caleffi iSolar 3 controller.

Room-temperature canola oil is pumped from a 1,500-gallon storage tank into the heat-exchanger tank. The oil is then heated by the solar-heated glycol solution running through the heat exchanger. To make a batch of biodiesel, 100 gallons of heated oil are drawn off the top of the exchanger tank using a metered pump. If the oil isn’t warm enough, it is routed to a third, 100-gallon receiving tank, where an electric element can add heat. Usually, the solar-heated oil is warm enough to be pumped directly to the reactor chamber, where it is mixed with methanol and sodium methylate to create biodiesel.

Hurdles & Accomplishments

Because vegetable oil is less dense than water, the size of the collector bank was adjusted accordingly. The specific heat of canola oil is lower than that of water, so fewer collectors are needed to heat oil. Although the glycol collector loop used standard equipment, materials and pumps that were compatible with vegetable oil had to be used in the oil loop piping. Because the heat exchanger tank is holding oil, rather than rust-inducing water, it was fabricated from cheaper mild steel instead of stainless steel.

The unpressurized heat exchanger tank posed a challenge of how to refill the tank quickly with a minimum of manual controls. Accidentally overflowing the tank was a potential problem, so a float switch, which senses oil level and controls the fill pump, was installed. The lighter oil necessitated some experimentation, and required an oversized float and an oversized fill pump.

Canola oil has a much higher boiling point than water, so overheating is much less of a concern than it would be for a conventional water-heating system. Because hotter oil speeds up the chemical reaction, exceeding 185°F isn’t a problem. This gives the system a lot of flexibility for when the hot oil can be drawn out of the exchanger tank.

The system still needs overheating safeguards for when the plant is not operating, to protect the collector loop and avoid breakdown of the glycol. When the collector loop reaches the high-limit temperature setting, the iSolar3 controller operates a valve to divert hot glycol to a fan/coil heater, which provides some limited space heating for the building. With moderate ambient summer temperatures, overheating of the large well-ventilated building was not a concern.

Function & Performance

The system has functioned well, providing the facility with a constant supply of solar-heated oil and considerably speeding up production. When sizing the system, we considered both the present and future needs of the facility. The goal of making approximately 100,000 gallons of biodiesel per year suggested a need for the system to heat 400 gallons of canola oil per working day. From there, we developed a system design and specified the collector array’s size. The system’s nine solar thermal collectors are capable of heating 200 gallons of water per day (on average) to the target temperature of 185°F. The specific heat of canola oil is about 45% of the specific heat of water and, as such, it takes less energy to raise the temperature of oil compared to water.

The facility’s current production is close to 200 gallons per day. Excess heat produced by the collectors is used to heat the oil beyond its target temperature and to supplement space heating for the building. Since canola oil has high heat tolerance, and the system has safeguards to protect it from overheating, we were able to size the system for anticipated future production levels.

The system provides 100% of the current heating of canola oil, and will continue to do so until production increases require more than 400 gallons of oil per day. When they get up to 400 gallons per day, better scheduling will be required to heat as much oil as possible with solar.

Doon hopes to have a grid-tied PV system installed at the plant to offset some or all of the plant’s electrical loads. Other solar thermal applications have also been discussed, but as of yet, there are no definite plans. Doon would like add a solar thermal project to heat the glycerin by-product enough to liquefy it, so that it can be burned in the plant’s waste oil heaters that provide the space heating for the building. Currently, the facility does not have a good market for the glycerin by-product, so Doon would like to find a way to use the product as an energy source.

The CCBD has funded its production equipment largely through about $600,000 in grant money, but the project has had a larger effect within the community. Gallegos’ original vision was one of local economic development, and the plant has created a new market for local farmers. It has created long-term jobs, and products that are made and sold locally. Farmers can buy the by-product feed meal, and their dollars stay in the community rather than being sent off to non-local feed companies. And making their fuel locally means even more money stays out of the hands of the oil companies, and instead is being pumped back into the local economy.

The addition of a solar thermal system takes another step toward keeping local money close to home. CCBD has shown that even a small rural community can create something with a lasting impact through the power of renewable energy.

Access

Laura Mezoff Christy is the vice president of Solar Gain Services (www.sgsrenewables.com), a solar installation and consulting company that focuses on specialized solar thermal and PV systems. She holds master’s degrees in architecture and city and regional planning from U.C. Berkeley.